An interesting decision. By breaking the queenside, White gains important squares for the knight.
16... f8e8 This type of position is sometimes seen in the Grunfeld Defense. White has the pair of bishops and a strong passed pawn, but Black is not without chances with a queenside pawn majority and the idea of blockading the pawn with Ne8-d6 or attacking it with Rad8. 17. d1d2  17... a8d8  18. a3c2 Both sides play natural moves. The knight returns to a better position. 18... d7f8 Preparing to attack the d5-pawn and maybe play Nf8-e6, exploiting the pin. There are alternatives.